Presently available solid state microelectronic devices consist of microcircuits with discrete circuit elements such as monolithic integrated circuits, transistors, diodes, resistors, capacitors, transformers, and conductors mounted on an insulating substrate. Thin film hybrid microcircuits are formed by vapor deposition of conductors, such as copper and gold, and resistors, such as tantalum, nichrome, and tin oxide onto a passive or insulating substrate such as silicon dioxide. An exact conductor pattern is obtained by masking or photolithographic etching. The entire circuit is subsequently encased with an epoxy dip to protect against moisture and contamination.
Modern integrated circuit devices, even highly miniaturized very large scale integrated devices (VLSI), are responsive only to electrical signals. There is now considerable interest in interfacing microelectronic devices with chemical and biological systems and it is therefore highly desirable to provide a microelectronic device that is responsive to such chemical or biological inputs. Typical applications for these devices include sensing of changes in pH and molar concentrations of chemical compounds, oxygen, hydrogen, and enzyme substrate concentrations.
Applicant is not aware of any apparatus or system which allows a direct interface between a microelectronic device sensitive to chemical inputs and a microminiature electrical circuit. Devices have been made on a larger scale which are sensitive to chemical input. These devices include such well known apparatus as pH sensors. Work in this area has recently centered around the use of electroactive polymers, such as polypyrrole or polythiophene. These compounds change conductivity in response to changes in redox potential. Recently, a polymeric semiconductor field effect transistor has been disclosed in a Japanese patent, 58-114465. As described in this patent, polymers such as trans-polyacetylene, cis-polyacetylene, polypyrrole, and polyvinyl phenylene have been used as inexpensive substitutes for single crystal silicon or germanium in making a semiconductor field effect transistor. There is no recognition of the unique properties of these polymers in this patent and, in fact, the polymers are treated as semiconducting material even though the properties of the polymers are distinctly different from that of silicon or germanium. The polymers are used as substitutes for semiconducting materials sensitive to electrical signals for uses such as in memory storage. Disadvantages to the FET as disclosed are that it is unstable and has a short useful life.
It is therefore an object of the present invention to provide a process for producing microelectronic devices responsive to chemical input which can be incorporated into microelectronic systems which are responsive to electrical input.
A further object of the present invention is to provide a process for constructing molecule-based microelectronic devices on silicon substrates which can easily be integrated with solid state silicon devices for signal processing.
Still another object of the invention is to provide small, sensitive, and specific microelectronic devices with very low power requirements.
A further object of the invention is to provide diodes, transistors, sensors, surface energy storage elements, and light-emitting microelectrode devices which can be controlled by molecular-level changes in electroactive polymer components.